From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [PATCH 2/4] rtmutex: add BUG_ON if a task attempts to block on two locks Date: Fri, 09 Jul 2010 20:30:25 -0400 Message-ID: <1278721825.1537.171.camel@gandalf.stny.rr.com> References: <1278714780-788-1-git-send-email-dvhltc@us.ibm.com> <1278714780-788-3-git-send-email-dvhltc@us.ibm.com> Reply-To: rostedt@goodmis.org Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Eric Dumazet , John Kacur , Mike Galbraith , linux-rt-users@vger.kernel.org To: Darren Hart Return-path: In-Reply-To: <1278714780-788-3-git-send-email-dvhltc@us.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Fri, 2010-07-09 at 15:32 -0700, Darren Hart wrote: > rtmutex proxy locking complicates the logic a bit and opens up > the possibility for a task to wake and attempt to take another > sleeping lock without knowing it has been enqueued on another > lock already. Add a BUG_ON to catch this scenario early. > > Signed-off-by: Darren Hart > Cc: Thomas Gleixner > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Eric Dumazet > Cc: John Kacur > Cc: Steven Rostedt > Cc: Mike Galbraith > --- > kernel/rtmutex.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c > index baac7d9..22f9d18 100644 > --- a/kernel/rtmutex.c > +++ b/kernel/rtmutex.c > @@ -459,6 +459,9 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, > top_waiter = rt_mutex_top_waiter(lock); > plist_add(&waiter->list_entry, &lock->wait_list); > > + /* Tasks can only block on one lock at a time. */ > + BUG_ON(task->pi_blocked_on != NULL); WARN_ON may be better. Since it may not cause a system crash or other huge bug if it is not true. -- Steve > + > task->pi_blocked_on = waiter; > > raw_spin_unlock(&task->pi_lock);